[verified] - How To Repair Rotted Window Sills

He brushed the hardener into every pore of the cavity. It soaked in, sizzling faintly as it bonded with the remaining cellulose. After an hour, the soft edges turned rock-hard.

When you think you’ve removed enough rot, remove another half-inch into the healthy wood. Rot is like an iceberg; what you see is less than what’s there. Chapter Three: The Hardener and the Filler Hendricks vacuumed out the cavity and let it sit for a day with a small fan aimed at it. Wood must be bone-dry before repair.

He brushed on an exterior oil-based primer, then two topcoats of satin latex. But the real secret came last: he did not caulk the bottom edge of the sill where it met the brick. Many people make that mistake. Caulk there traps water. Instead, he left a ⅛-inch gap—a “weep path”—so any future moisture could escape. how to repair rotted window sills

By the time he noticed the problem, it wasn’t a drip anymore. It was a soft, crumbly patch of wood near the outer edge—dark brown, spongy to the touch, and flecked with the fine orange dust of dry rot.

Then he mixed the two-part epoxy filler. It smelled like a chemistry lab and felt like warm taffy. He pressed it into the cavity with a putty knife, overfilling slightly, mounding it above the original surface. He let it cure for a full 24 hours. Patience, he reminded himself. Rot took years. Epoxy takes a day. Now came the art. The cured epoxy was harder than the original oak. Hendricks pulled out a block plane and a rasp. He shaved the epoxy down to the level of the old sill, then used the rasp to carve the subtle front slope—the “drip edge”—that shed water away from the glass. He brushed the hardener into every pore of the cavity

Shape the repair to shed water. The sill must slope away from the house, about 5 degrees. Any backward tilt is a suicide pact. Chapter Five: The Armor Hendricks sanded the whole sill smooth—old wood and new epoxy together—with 120-grit, then 220. Dust flew. The patch became indistinguishable from the original under a coat of primer.

First, he cut away the old caulk and glazing putty from the bottom of the lower sash. Then, with a oscillating multi-tool (though a sharp chisel would do), he cut a clean straight line about an inch past the visible rot on each side. The cut was vertical, maybe half an inch deep into good wood. When you think you’ve removed enough rot, remove

Finally, he replaced the broken glazing bead that had started the whole tragedy, bedding it in fresh glazing compound. Three weeks later, a nor’easter hammered the coast. Hendricks sat in his armchair, drinking tea, watching the rain sluice down the glass and dance off the new sill. He walked over, ran a finger along the underside. Bone dry.